The present invention relates to a cooling apparatus capable of conducting cooling so as to obtain the target temperature of a semiconductor device that comprises a plane-like surface and generates heat to above the target temperature and has the temperature of the one surface rising when electric current is passed therethrough.
A burn-in apparatus for semiconductor devices (referred to hereinbelow as “devices”) is generally known in which a multiplicity of devices are mounted on burn-in boards, the boards are stacked in multiple stages in a temperature controlled chamber, electric current is passed through the devices, and hot air with a temperature adjusted to the fixed temperature, for example 125° C., is caused to flow parallel to the burn-in boards inside the chamber and circulate, while uniformly cooling the multiplicity of devices (see, for example, Patent References 1, 2). With such a burn-in apparatus, in the case of conventional devices, the internal temperature of the devices generating heat when a current is passed therethrough is adjusted to a temperature appropriate for the burn-in test, which is about 150° C., correspondingly to the temperature of the circulating hot air and a burn-in test of the multiplicity of devices can be conducted with good efficiency.
Furthermore, Patent Reference 3 describes, as the conventional technology, that detecting the temperature inside the chamber and maintaining it at a constant level alone does not directly control the temperature of the device itself and, therefore, a diode is formed in a hollow space of a semiconductor chip and the junction temperature of the semiconductor chip is evaluated based on the electric characteristics of the diode (see the same Patent Reference 3).
Furthermore, the Patent Reference 3 also suggests a burn-in test apparatus in which a wiring section for temperature measurements is disposed over the entire integrated circuit section of each semiconductor chip, the average temperature of the chip is detected via a connection pad provided similarly to the connection pad for current supply to the integrated circuit section, the air with adjusted temperature is supplied from air-blow fans disposed correspondingly to each semiconductor chip in a temperature adjusting apparatus, and the air flow amount supplied to each chip is controlled so that the average temperature of the chip becomes the target burn-in temperature.
On the other hand, in recent years, devices generating a large amount of heat, for example, up to about 300 W when an electric current is passed therethrough, have appeared on the market and the burn-in apparatuses and cooling apparatuses for printed substrates on which such devices generating a large amount of heat are mounted have to be adapted to conduct the burn-in test of such devices that generate a large amount of heat. However, with the above-described conventional apparatus of a generic hot air circulation system, because the one surface of the device is cooled directly using one type of air, the cooled surface area and/or the amount of cooling air is insufficient and the large amount of heat generated by the device cannot be removed.
Accordingly, as a cooling apparatus for a printed substrate mounted with devices, including devices that generate a large amount of heat, a cooling apparatus for semiconductor elements has been suggested wherein cooling air is made to flow from one blower serving as a common air cooling means to a cooling chamber above the printed substrate onto which elements generating a small amount of heat and elements generating a large amount of heat, which correspond to the devices, have been mounted, cylindrical and teacup-shaped accordion fins are brought into contact with one portion of each surface of the elements generating a small amount of heat and elements generating a large amount of heat and via these fins the elements are collectively cooled, and with respect to the elements generating a large amount of heat, high pressure air is sent into the teacups through a nozzle of a high pressure air passage by a small high-pressure fan (see Patent Reference 4).
With the teacup-shaped fins of this cooling apparatus, because the air on the inside and on the outside of the fin is separated by the fin, the air on each side does not mix directly and so the air on each side can be made to perform its cooling function independently, but because one integrated fin is touching a portion of an element surface and is spread out so as to occupy a large volume: the flow of air in the cooling chamber is considerably disrupted; since there is only one fin, even though it is accordion-shaped, the area that is cooled is small; the area of the base portion of the fin connected to the contact section that touches the surface of the element is small and this is only touching one portion of the element surface; and although the air flow is at higher pressure than it would be with a blower, because it is being pushed by a high pressure fan, the speed is not great. For reasons such as these, in the end the cooling effect for the element generating a large amount of heat is not sufficient.
Also, similarly, as a cooling apparatus for a printed substrate mounted with devices, including devices that generate a large amount of heat, a heat sink direct air injection system has been suggested wherein cooling air is commonly supplied, similarly to the above, to a cooling chamber above a printed substrate mounted with heat sinks, including heat sinks generating a large amount of heat that correspond to devices that generate a large amount of heat, and pressurized air from a blower is supplied through a small air duct so that via an orifice of a size that corresponds to the amount of heat generated by the device the air falls directly from the one surface of the device toward a central space provided in the device (see Patent Reference 5).
With this system, because air inside and outside of the heat sink has been separated by the central space, the air on each side does not mix directly and so mutually independent cooling effects can be produced, but such a system can only be used for special devices that have a hole such as a central space, and although air flow is at higher pressure than it would be with a blower, because it is being pushed by an air blower that has a discharge pressure limited to 100 KPa or so, the speed is not great. For reasons such as these, in the end the cooling effect for the elements generating a large amount of heat is not sufficient.
Also, an air injection type temperature control apparatus is known, wherein air that has been compressed by a compressor and cooled is sprayed by air injection nozzles arranged on both sides of a device, and both sides of each individual object are cooled directly (see Patent Reference 6). However, this apparatus entails the following problems: because it is configured to cool both sides of the device, it cannot be adapted to a usual burn-in apparatus in which one surface side of the device serves as a mounting surface for a connector providing for electric connection to the device; because the entire amount of the heat generated by the device is removed only by the amount of air hitting the surfaces, it is difficult to control the temperature of the device accurately enough by just controlling this amount of air; because the sprayed air falls on the surfaces of the device directly, these surfaces are affected thereby, e.g., become stained or discolored.
[Patent Reference 1] Japanese Patent Application Laid-open No. H8-211122 (FIG. 1 and relevant explanation in the specification).
[Patent Reference 2] Japanese Patent Application Laid-open No. H11-231943 (FIG. 1 and Par. No. 25 in the specification).
[Patent Reference 3] Japanese Patent Application Laid-open No. 2000-97990 (FIG. 4 and Par. Nos. 3, 4 in the specification; FIGS. 1 and 2 and relevant explanation in the specification).
[Patent Reference 4] Japanese Patent Application Laid-open No. H1-28896 (especially the second figure and relevant explanation)
[Patent Reference 5] U.S. Pat. No. 4,851,965 (especially the second and third figures and relevant explanation)
[Patent Reference 6] Japanese Patent Application Laid-open No. H4-321113 (FIG. 1 and relevant explanation in the specification).